Compilation of revised ages of volcanic units in the San Juan Mountains, Colorado; recalculated K-Ar age determinations using IUGS constants

Previously published K-Ar age determinations for the middle to late Tertiary San Juan volcanic field have been recalculated using the 1977 IUGS constants. Revised ages, original analytical data, and brief sample descriptions are presented in table 2 for all available dated volcanic units. A generalized stratigraphic column is also included to facilitate comparison of the ages of major volcanic events among more recent publications and previously published papers. No attempt has been made to assess the validity of individual K-Ar ages and, for the purpose of interpretation, the reader is referred to the original source.